The field of the invention is that of apparatus for producing and controlling charged particle beams, and, in particular, apparatus for producing and controlling electron beams as in cathode ray or television tubes.
At present two primary systems of obtaining more brightness in a cathode-ray tube exist: the use of new, more efficient light-emitting phosphors; and an increase in the accelerating voltage. Both of these systems have approached their maximum efficiency and significant breakthroughs are not expected. However, brightness could also be increased by illuminating a complete line of video information simultaneously.
During the 1930's attempts were made by inventors such as von Bronk and Jefree to build large-screen television devices that would project a single line of video information simultaneously. The only successful machine was the "Scophony" large-screen television projector of Jefree. This projector used a special "supersonic" light valve with split-focus which, through the vibration of a piezoelectric crystal, set up a train of sonic waves in the liquid contained in a special tube or light cell. See, e.g., J. Stieger, "The Design and Development of Television Receivers using the Scophony Optical Scanning System," Proceedings of the I.R.E. (August 1939). A train of waves in the light cell had light and dark elements and represented a line of video information traveling in one direction. It was immobilized by means of a mirror wheel rotating rapidly in the opposite direction. As the light from an arc lamp went through the light cell, the light output of the light cell was modulated by the light and dark elements. A second rotating mirror wheel produced the frame scan. Tremendous brilliance could, therefore, be obtained from an ordinary light source. However, this process depended on mechanical devices and was soon abandoned. A wholly electronic system for producing simultaneous projection of single lines of video information in a cathode ray tube would offer significant advantages in reliability and brightness.